1. Field of the Invention
The invention relates to a discharge lamp, in which an emission or irradiation is obtained through resonance lines, which are emitted from ions in an excitation state.
2. Background of the Disclosure
Conventionally in the case of a known discharge lamp an emission through spectral lines is used, which are emitted within an arc formed between electrodes at transitions of atoms or ions from one excitation sate to another excitation state or ground state.
Resonance lines, which are among the emission spectral lines, which are emitted at transitions of atoms or ions from one excitation state into a ground state, due to their high transition probability, generally have a high radiation factor, potentially.
Lamps, whose irradiated resonance lines are short-wave ultraviolet rays, therefore have a very high industrial value. Lamps with a high output of short-wave ultraviolet rays are e.g. necessary in photochemical industries, in the manufacture of semiconductor devices, etc. There are adequate possibilities for covering such needs.
However, in the presently used discharge lamps it is considered disadvantageous that there is unavoidably a so-called self-absorption phenomenon. This means that optically-thick spectral lines such as resonance lines, which are emitted within the arc from the atoms or ions in the excitation state, are absorbed to a high degree by similar atoms or ions. These atoms or ions simultaneously coexist in a ground state. As a consequence of this the radiation light to be obtained through the resonance lanes is not radiated to the outside with a high radiation intensity from the lamp and in practice such a lamp is unusable.
For example, in the case of a mercury arc lamp of the short arc type, resonance lines with wavelength of 185 nm and 254 nm emitted by g in an excitation state within a high temperature arc are absorbed by Hg, which is present in a part having a low temperature in a periphery of the arc and is in a ground state. Therefore the resonance lines are only radiated to the outside from the lamp to a very small extent.
In the case of discharge lamps, emitted light intensity can normally be increased by raising the partial pressure of the major emission material and by increasing the temperature of the emission atoms of ions during operation. However, resonance lines can only be emitted by reducing the self-absorption phenomenon. For example, resonance lines with the wavelength 254 nm, which are emitted by Hg, only have an adequate intensity for industrial uses in the case of a mercury arc lamp with an extremely low pressure of approximately 1.times.10.sup.-1 Pa.
Thus, for the reason indicated hereinbefore, there is neither a usable medium pressure lamp, nor a usable high pressure lamp with a suitably high output of short wave ultraviolet, rays.